The present disclosure is generally related to toners including polyester resins, and in embodiments, to toners made by emulsion aggregation (EA) and coalescence processes. The toners herein, in embodiments, are environmentally friendly, as they do not use the endocrine disruptor bisphenol A. The toners herein, in embodiments, provide improved carbon/oxygen ratios and, in embodiments, exhibit stable charge and low relative humidity sensitivity.
Emulsion/aggregation/coalescence processes for the preparation of toners are illustrated in a number of patents, the disclosures of each of which are incorporated herein by reference in their entirety, such as U.S. Pat. Nos. 5,290,654, 5,278,020, 5,308,734, 5,370,963, 5,344,738, 5,403,693, 5,418,108, 5,364,729, and 5,346,797; and also of interest may be U.S. Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658; 5,585,215; 5,650,255; 5,650,256; 5,501,935; 5,723,253; 5,744,520; 5,763,133; 5,766,818; 5,747,215; 5,827,633; 5,853,944; 5,804,349; 5,840,462; 5,869,215; 5,863,698; 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488; 5,977,210; 5,994,020; 6,020,101; 6,130,021; 6,120,967; 6,628,102; 6,664,015; 6,780,560; 6,818,723; 6,824,944; 6,830,860; 6,849,371; 7,208,253; 7,329,476; 7,402,371; 7,416,827; 7,425,398; 7,442,740; and U.S. Patent Application Publication No. 2008/0107989.
Thermal properties are a consideration in the design of a suitable toner. Toners should be designed to help prevent the occurrence of “hot offset.” The resin useful in the toner should be amorphous, in embodiments, with a glass transition temperature from about 50° C. to about 65° C., in embodiments from about 52° C. to about 60° C. The softening point, as measured by a Mettler Softening point apparatus, should be from about 108° C. to about 112° C. for high gloss application, or greater than about 125° C. for matte applications.
Many current polyester based toners are derived from the bisphenol A monomer. Bisphenol A has been identified as an endocrine disrupter and possible carcinogen, resulting in adverse developmental health effects. Several European Countries, as well as Canada and several U.S. states, have suggested or implemented a ban of bisphenol A.
Toners that do not use bisphenol-A polyester resins are known, such as those derived from aliphatic glycols and terephthalic acids. Although these resins may provide suitable fusing performance, the toners may display poor electrical performance due to their hydrophilic nature and low carbon/oxygen (C/O) ratio. As a design rule for obtaining good electrical performance, a successful model that has been used in polyester resins is to calculate the C/O ratio of the resin. For example, known toners using bisphenol A and/or styrene based resins have been shown to have a C/O ratio of from about 4.2 to about 5.5. These toners show stable charge and low RH sensitivity. Previous designs using terephthalic-glycol based resins showed a C/O ratio of from about 1.5 to about 2, and displayed poor electrical and RH sensitivity results.
It remains desirable to provide a toner including a polyester resin, which is not derived from the endocrine disruptor bisphenol A. It is further desirable to provide a polyester resin toner which has a suitable glass transition temperature, softening point, C/O ratio, improved electrical characteristics, and RH sensitivity.